It is known that urine pH can be interpreted to provide information concerning the physiological state of an animal. For instance, the urine of a healthy cat has a pH ranging from about 6.4 to about 6.8. Many feline diseases are accompanied by a shift in urinary pH from the normal pH range to an acidic or alkaline condition. Abnormal urine pH may indicate viral-infections, cystitis, secondary infections from procedures, such as spaying or hysterectomies, complications from feline leukemia and other pathologies. Many of the common causes of abnormal feline urinary pH are referred to cumulatively as Feline Lower Urinary Tract Disease (FLUTD) or feline urological syndrome (FUS).
Besides being symptomatic of a variety of diseases, abnormal Urinary pH has its own associated pathology, such as, the formation of uroliths or crystals associated with FLUTD. A pH reading above 7 may give rise to the growth of magnesium ammonium phosphate crystals, or struvites, while a pH below 6.4 is conducive to the formation of calcium oxalate crystals. Each of these conditions is uncomfortable and unhealthy for the effected animal. It would therefore be desirable for cat owners to be alerted to abnormal urine pH as soon as possible such that they can seek early diagnosis and treatment of their cat's potential health problems by a qualified veterinarian, thus sparing the cat from pain, illness and/or death. A product and method for monitoring urinary pH would also be valuable as part of a program for cats who are recuperating from or have been treated for disease.
U.S. Pat. No. 5,143,023 describes a litter for the accumulation of animal urine having a visual indicator chemically bound to the litter base material. The litter is used to ascertain the pH of an animal's urine to indicate potential pathology. The patent teaches that the litter base material must have the ability to exchange ions in order to bind the pH indicating molecules to the litter base material while leaving the pH-sensitive reactive groups available to indicate the presence of ions. U.S. Pat. No. 5,143,023 also proposes neutralizing the litter base material, e.g., clay, to prevent the indicator from interacting with the base material upon which it is directly deposited. U.S. Pat. No. 5,143,023 suggests that more than one indicator can be used, but advises that consumer-directed litters be limited to two indicators. The examples provided in U.S. Pat. No. 5,143,023 test for one pH threshold and exhibit one color change.
Another known animal urine pH testing kit utilizes strips of paper treated with a chemical reagent. To perform a test, the strips are placed on top of or in the cat litter in a litter box. When the cat urinates on the strips, the strips exhibit a color change. Because the strips are physically distinct from the cat litter, they interfere with the cat's normal use of the litter box such that the cat may avoid urinating on the test strips in the litter box. The strips are preferably removed from the litter box after the test and compared to a graduated color scale. The necessity of retrieving the used litmus paper from the litter box and holding a color scale in proximity to it is inconvenient and unpleasant. Perhaps more importantly, the testing of urine pH by introducing litmus paper to a litter box is subject to false pH readings due to the pH effect of the litter on the urine solution contacting the litmus paper. Furthermore, litmus paper typically exhibits only one color change to indicate a shift of pH across a single pH threshold. It is therefore an object of the present invention to provide a pH indicator material that is accurate and compatible with cat litter such that a cat does not avoid the indicator, is easy to use and is calibrated to provide pronounced color indicia associated with acidic, normal and alkaline urine pH.